Let us now look at the origin of the ultrafast optical response of the Ag-nCdTe hybrid colloid. In a metal-semiconductor hybrid, when a metal NP interacts with semiconductor QD, the optical response of the combined nanostructure is expected to be very different from that of the individual components. When excited at the LSPR, the local field near the metal NP can be much higher than the applied; such a large field can increase the absorption in semiconductor QD[1]}, [2]}. It is also possible that excited carriers may get transported from metal NP to semiconductor QD or vice versa[3]}. Additionally, energy exchange processes like foster resonance energy transfer (FRET) and plasmon-induced resonance energy transfer (PIRET) are also possible in the hybrid system[4]}, [5]}. Coupling between the metal NP and semiconductor QD is also known to introduce additional defect states in the hybrid nanostructures[6]}, [7]}. The individual contribution from each of these above mentioned processes to the optical response of the hybrid depends on the shape, size and material of the individual components, the properties of linking molecules and their spatial distribution. To understand the origin of the optical response of the hybrid arising due to their synergistic interaction, it is necessary to understand changes in the LSPR of Ag NP due to the presence of CdTe QDs.
